Legal claims defining the scope of protection. Each claim is shown in both the original legal language and a plain English translation.
1. An operation method of an access point (AP) comprising: determining at least one neighboring AP to perform interference alignment (IA) in cooperation with the AP; receiving first channel information between at least one station associated with the AP and the AP and second channel information between the at least one station and the at least one neighboring AP from the at least one station; acquiring IA information based on the first channel information and the second channel information; and transmitting data based on the IA information, wherein the transmitting comprises: transmitting an IA Synchronization (Synch) frame to the at least one neighboring AP; and transmitting downlink data simultaneously with the at least one neighboring AP during a transmission duration comprised in the IA Synch frame.
In a wireless network, an access point (AP) coordinates with neighboring APs to reduce interference using interference alignment (IA). The AP first identifies neighboring APs for IA. It then receives channel information from associated stations, including the channel between the station and the AP itself, and the channel between the station and each neighboring AP. Based on this information, the AP calculates IA parameters and transmits data using IA. The AP sends an IA Synchronization (Synch) frame to the neighboring APs. During a specified transmission period within the IA Synch frame, the AP and the neighboring APs transmit downlink data simultaneously to their respective stations.
2. The operation method of claim 1 , wherein the receiving comprises: transmitting an IA Null Data Packet (NDP) Announcement frame comprising an AP list and an station information (STA Info) list to the at least one neighboring AP and the at least one station; transmitting an NDP to the at least one station; and transmitting an AP-Poll frame of a predetermined type to a next neighboring AP on the AP list.
The AP initiates the channel information gathering process by sending an IA Null Data Packet (NDP) Announcement frame to neighboring APs and associated stations. This frame includes a list of APs involved in IA and information about the stations. The AP then transmits an NDP to each station, allowing them to estimate the channel characteristics. Finally, the AP sends a special type of AP-Poll frame to the next neighboring AP in its AP list, triggering that AP to begin its own channel estimation process.
3. The operation method of claim 2 , wherein a neighboring AP corresponding to an address of a Receiver Address (RA) field comprised in the AP-Poll frame of the predetermined type resets a Network Allocation Vector (NAV), transmits the IA NDP Announcement frame to stations associated with the neighboring AP, and transmits an NDP to the stations.
Upon receiving the special AP-Poll frame, a neighboring AP resets its Network Allocation Vector (NAV), preventing other transmissions. It then transmits an IA NDP Announcement frame to its associated stations, followed by an NDP. This allows those stations to estimate the channel characteristics between themselves, the neighboring AP, and other APs in the IA group, thus collecting the required channel information. The neighboring AP then proceeds with its own IA calculations and data transmission.
4. The operation method of claim 1 , wherein the receiving comprises: transmitting an IA Beamforming (BF) Report Poll frame to the at least one station; receiving a BF Report frame comprising the first channel information and the second channel information from the at least one station; and transmitting an AP-Poll frame of a predetermined type to a next neighboring AP on an AP list.
Instead of using NDPs, the AP can use an IA Beamforming (BF) Report Poll frame to request channel information. The AP sends this frame to its associated stations. In response, the stations send back a BF Report frame containing both the channel information between the station and the AP, and the channel information between the station and the neighboring APs. After receiving the BF Reports, the AP transmits a special type of AP-Poll frame to the next neighboring AP in the AP list, similar to the NDP method.
5. The operation method of claim 4 , wherein the BF Report Poll frame comprises a Segment Retransmission Bitmap field for the AP and a Segment Retransmission Bitmap field for the at least one neighboring AP.
The IA Beamforming (BF) Report Poll frame includes "Segment Retransmission Bitmap" fields. One field is for the AP itself, and another is for the neighboring APs. These bitmap fields allow the AP to request specific segments of channel information to be retransmitted if some data was lost or corrupted during the initial transmission of the BF Report frame from the stations. This ensures that all required channel information is accurately received.
6. The operation method of claim 4 , wherein a neighboring AP corresponding to an address of an RA field comprised in the AP-Poll frame of the predetermined type resets a Network Allocation Vector (NAV), transmits the IA BF Report Poll frame to stations associated with the neighboring AP, and receives a BF Report frame from the stations.
When a neighboring AP receives the special AP-Poll frame (following the beamforming report method), it resets its NAV. It then sends an IA Beamforming (BF) Report Poll frame to its associated stations, requesting them to send BF Report frames. The neighboring AP then receives the BF Report frames from its stations. This allows the neighboring AP to gather the necessary channel information for its own IA calculations.
7. The operation method of claim 4 , wherein the receiving further comprises: determining a neighboring AP which needs to additionally receive a BF Report frame; and transmitting the AP-Poll frame of the predetermined type to the determined neighboring AP.
If the AP determines that it needs to receive additional BF Report frames from neighboring APs, it transmits the special AP-Poll frame to those specific neighboring APs. This allows for selective channel information updates, ensuring that the AP has the most up-to-date information for interference alignment, and can handle scenarios where channel conditions change dynamically or some reports are initially incomplete.
8. The operation method of claim 1 , wherein the transmitting further comprises: transmitting a multicast Request to Send (RTS) frame to the at least one neighboring AP; and receiving a multicast Clear to Send (CTS) frame from the at least one neighboring AP.
Before simultaneous downlink data transmission, the AP transmits a multicast Request to Send (RTS) frame to all the neighboring APs involved in the IA process. The AP then receives a multicast Clear to Send (CTS) frame from each of those neighboring APs. This RTS/CTS exchange serves as a contention mechanism, ensuring that all participating APs are ready to transmit simultaneously and minimizes collisions due to hidden nodes.
9. The operation method of claim 1 , wherein a neighboring AP corresponding to an address of an AP Basic Service Set Identification (BSSID) field comprised in the IA Synch frame resets a Network Allocation Vector (NAV) and transmits downlink data after SIFS using IA.
Upon receiving an IA Synchronization (Synch) frame, a neighboring AP resets its Network Allocation Vector (NAV), preventing other transmissions. It then transmits its own downlink data, using interference alignment (IA), after a Short Interframe Space (SIFS) period. The IA parameters used in the transmission are determined by the channel information previously exchanged and the IA calculations.
10. The operation method of claim 1 , wherein the transmitting further comprises transmitting a Block Acknowledgement (Ack) Request (BAR) frame to the at least one station; receiving a Block Ack (BA) frame from the at least one station; and transmitting an AP-Poll frame of a predetermined type to a next neighboring AP based on order information on APs comprised in an IA Synchronization (Synch) frame.
After the simultaneous downlink data transmission, the AP sends a Block Acknowledgement Request (BAR) frame to its associated stations, requesting confirmation of received data. The AP then receives a Block Ack (BA) frame from the stations. Following this, the AP transmits a special AP-Poll frame to the next neighboring AP based on the order specified in the initial IA Synchronization (Synch) frame. This facilitates a coordinated turn-taking approach.
11. The operation method of claim 10 , wherein a neighboring AP corresponding to an address of a Receiver Address (RA) field comprised in the AP-Poll frame of the predetermined type resets a Network Allocation Vector (NAV), transmits the BAR frame to stations associated with the neighboring AP, and receives the BA frame from the stations.
The neighboring AP, after receiving the special AP-Poll frame, resets its Network Allocation Vector (NAV). It then transmits a Block Acknowledgement Request (BAR) frame to its associated stations, requesting confirmation of data it previously sent. The neighboring AP then receives the Block Ack (BA) frames from its stations, completing its part of the coordinated transmission sequence.
12. The operation method of claim 1 , wherein the transmitting further comprises: receiving an AP-Poll frame of a predetermined type from the at least one neighboring AP; determining neighboring APs which need to additionally transmit data based on a more data bit comprised in the AP-Poll frame of the predetermined type; and transmitting an IA Synch frame to the determined neighboring APs.
An AP can also receive the special AP-Poll frame from a neighboring AP. Based on the "more data" bit included in the AP-Poll frame, the AP determines if any other neighboring APs need to transmit additional data. If so, the AP transmits an IA Synch frame to those neighboring APs, signaling them to begin their own data transmission using interference alignment (IA). This creates a dynamic chain of transmission.
13. The operation method of claim 1 , wherein the first channel information is channel information estimated from a Null Data Packet (NDP) received from the AP directly associated with the at least one station, and the second channel information is channel information estimated from an NDP received from the at least one neighboring AP which is not associated with the at least one station but belongs to the same IA transmission group.
The channel information used for IA calculations consists of two parts. The first part, "first channel information," is estimated by the station from a Null Data Packet (NDP) received directly from its associated AP. The second part, "second channel information," is estimated by the same station from an NDP received from a neighboring AP that is part of the same IA transmission group but not directly associated with the station.
14. An operation method of an access point (AP), comprising: determining at least one neighboring AP to perform interference alignment (IA) in cooperation with the AP; receiving first channel information between at least one station associated with the AP and the AP and second channel information between the at least one station and the at least one neighboring AP from the at least one station; acquiring IA information based on the first channel information and the second channel information; and transmitting data based on the IA information, wherein the determining comprises: transmitting an IA-Request to Send (RTS) frame comprising a candidate AP list to the at least one neighboring AP; transmitting a Clear to Send (CTS)-Poll frame to a first neighboring AP comprised in the candidate AP list; and determining the first neighboring AP as an IA participant node when an IA-CTS frame is received from the first neighboring AP.
To determine which neighboring APs to include in the IA process, the AP first transmits an IA-Request to Send (RTS) frame containing a list of candidate APs to those neighbors. Then, the AP sends a Clear to Send (CTS)-Poll frame to the first neighboring AP on the candidate list. If the AP receives an IA-CTS frame in response from that neighbor, the AP determines that this neighbor will participate in interference alignment and includes it in the IA transmission group.
15. An operation method of an access point (AP), comprising: determining at least one neighboring AP to perform interference alignment (IA) in cooperation with the AP; receiving first channel information between at least one station associated with the AP and the AP and second channel information between the at least one station and the at least one neighboring AP from the at least one station; acquiring IA information based on the first channel information and the second channel information; and transmitting data based on the IA information, wherein the acquiring comprises: generating IA calculation information for the AP based on the first channel information and the second channel information; transmitting the IA calculation information for the AP to the at least one neighboring AP; and receiving IA calculation information for the at least one neighboring AP from the at least one neighboring AP.
In a wireless network, an access point (AP) coordinates with neighboring APs to reduce interference using interference alignment (IA). The AP first identifies neighboring APs for IA. It then receives channel information from associated stations, including the channel between the station and the AP itself, and the channel between the station and each neighboring AP. The AP generates its own IA calculation information based on this channel data. The AP transmits its IA calculation information to the neighboring APs and receives the IA calculation information from the neighboring APs. Based on all this information, the AP transmits data using IA.
16. The operation method of claim 15 , wherein when the IA calculation information for the at least one neighboring AP is received via a cable, expected data transmission duration for the at least one neighboring AP is further received.
When the IA calculation information from neighboring APs is received via a cable connection, the AP also receives the expected data transmission duration for each of those neighboring APs. This allows the AP to coordinate simultaneous transmissions more effectively, by taking into account the time needed for each AP to transmit its data. This is relevant for wired backhaul networks connecting the access points.
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December 5, 2017
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